Field of the Invention
This invention relates to desulphurisation materials and in particular desulphurisation materials comprising copper and zinc oxide.
Description of the Related Art
Hydrocarbon feedstocks intended for use in synthesis gas generation must first be desulphurised in order to protect sensitive downstream catalysts from deactivation. Sulphur removal is conventionally carried out using a combination of hydrodesulphurisation (HDS) catalysis (based typically on CoMo or NiMo catalysts) and zinc oxide based absorbents. The zinc-based absorbents are designed to capture H2S according to the following equation;ZnO+H2S→ZnS+H2O
The performance of ZnO based absorbents used for sulphur capture is a compromise between density and porosity. High density allows more ZnO to be loaded into a vessel on a unit volume basis, therefore increasing the theoretical sulphur pick-up available and potentially lengthening time between change-outs. However, in practice the low porosity and associated low surface area of such dense materials generates a kinetic barrier to the sulphiding process, which prevents a significant amount of the ZnO present in the reactor being utilised effectively.
This consideration has placed a practical upper limit on the density of current-generation ZnO based products used in commercial operation. This upper limit is in the region of 1.5 kg/l.